In a non-continuous magnetic tape system, magnetic tape is wound around one reel and retrieved from another reel by a tape transport system. This arrangement can be present in traditional reel-to-reel systems, two-reel cartridge systems and single reel cartridge systems.
In the case of non-continuous single cartridge systems, the supply reel for the magnetic tape medium is carried in the cartridge. The cartridge is capable of being easily loaded into the tape transport system for recording (writing) and reproducing (reading). The cartridge is also easily removed from the system for storage. A take-up reel or hub is permanently carried by the tape transport system.
For the purposes of this discussion, the reel which at any given time is discharging tape will be referred to as in an "unwinding condition", and the reel which at any given time is receiving tape will be referred to as in a "winding condition".
To make loading and removal of the cartridge as easy as possible, techniques have been developed for automatically threading the magnetic tape medium from the cartridge to the take-up reel and through the various stations of the tape transport system. One automatic threading system includes a semi-rigid leader tape (leader tape). One end of the leader tape is permanently attached to the take-up reel and the other end of the leader tape is attached to a leader block. The to-be-threaded magnetic tape in the cartridge includes a tape block attached to the free end of the magnetic tape.
To accomplish automatic threading, the cartridge is inserted into the tape transport system. Upon insertion of the cartridge, a cartridge engagement (and disengagement) mechanism moves the cartridge through a cartridge load path and positions the cartridge appropriately in the tape transport system. The tape block and leader block are then joined together by the block connection mechanism residing in the tape transport system. It is noted that the complexity and therefore the cost of the cartridge engagement mechanism is in large part a function of the complexity of the cartridge load path and how precisely the cartridge engagement mechanism must position the cartridge in the tape transport system. In addition, the complexity and therefore cost of the block connection mechanism is a function of the difficulty in forming the connection between the tape block and leader block.
After the leader block and tape block are joined, the take-up reel is then placed in a winding condition resulting in the leader tape being wrapped onto the take-up reel and the magnetic tape being pulled from the cartridge through the tape threading path of the tape transport system. During this operation, the joined tape block and leader block (joined blocks) travel through the threading path of the tape transport system and are eventually received by the take-up reel. Thus the leader tape and the joined blocks become the substrate for subsequent wraps of magnetic tape onto the take-up reel.
It is highly desirable for the substrate formed by the leader tape and joined blocks to be smooth and cylindrical in order to achieve proper packing of the magnetic tape on the take-up reel. If a smooth cylindrical substrate is not formed, creases could be formed in the subsequent layers of magnetic tape. This can cause problems in the reuse of the tape since magnetic transitions might occur at the creases making the resensing of the magnetic transitions less reliable.